1. Field of the Invention
The present invention relates to a fuel injection controlling system for an internal combustion engine which digitally computes the quantity of fuel required by the engine.
2. Description of the Prior Art
In the past, fuel injection controlling systems for internal combustion engines have been proposed in which in accordance with the principal engine parameters such as the air flow rate Q, the engine rpm N and the constant K corresponding to the air-to-fuel ratio (A/F) of the mixture, the required fuel quantity ##EQU1## of the engine is computed to control the fuel injection quantity. These systems employ an analog computing method and their control units are mainly composed of such elements as capacitors, resistors and transistors. Therefore, these conventional systems are disadvantageous in that the operation of the control unit is fluctuated by variations in a supply voltage and/or changes in ambient temperatures thus necessitating fine adjustments of the various parts of the control unit in accordance with the required characteristic of the engine, and moreover the accuracy of the control unit on the whole is deteriorated by the deterioration of the component elements with age.